Add buffered code-mode exec yields (#34441)

## What changed

- Add the experimental `code_mode_buffered_exec` feature.
- When enabled, default code-mode `exec` calls without an explicit
  `yield_time_ms` to 30 seconds instead of 10 seconds.
- Report the effective default in the model-visible `exec` tool description.

## Testing

- Verify that the generated tool description advertises the 30-second default
  when the feature is enabled.

GitOrigin-RevId: 0eea4d0105137f09050ce31aad18c25c79df6b2a

codex-rs/code-mode-protocol/src/description.rs

@@ -253,10 +253,14 @@ pub fn build_exec_tool_description(
     enabled_tools: &[ToolDefinition],
     deferred_tools: &[ToolDefinition],
     namespace_descriptions: &BTreeMap<String, ToolNamespaceDescription>,
+    default_exec_yield_time_ms: u64,
     code_mode_only: bool,
 ) -> String {
     let mut sections = Vec::new();
-    sections.push(EXEC_DESCRIPTION_TEMPLATE.to_string());
+    sections.push(EXEC_DESCRIPTION_TEMPLATE.replace(
+        "Defaults to 10000 ms.",
+        &format!("Defaults to {default_exec_yield_time_ms} ms."),
+    ));
     if !deferred_tools.is_empty() {
         sections.push(DEFERRED_NESTED_TOOLS_GUIDANCE.to_string());
     }
@@ -868,6 +872,7 @@ mod tests {
             }],
             &[],
             &BTreeMap::new(),
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
             /*code_mode_only*/ true,
         );
         assert!(description.contains(
@@ -879,8 +884,13 @@ bar"
 
     #[test]
     fn exec_description_mentions_timeout_helpers() {
-        let description =
+        let description = build_exec_tool_description(
-            build_exec_tool_description(&[], &[], &BTreeMap::new(), /*code_mode_only*/ false);
+            &[],
+            &[],
+            &BTreeMap::new(),
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
+            /*code_mode_only*/ false,
+        );
         assert!(description.contains("`audio(audioUrlOrItem:"));
         assert!(description.contains("`setTimeout(callback: () => void, delayMs?: number)`"));
         assert!(description.contains("`clearTimeout(timeoutId?: number)`"));
@@ -932,6 +942,7 @@ bar"
             ],
             &[],
             &namespace_descriptions,
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
             /*code_mode_only*/ true,
         );
         assert_eq!(description.matches("## mcp__sample").count(), 1);
@@ -972,6 +983,7 @@ bar"
             }],
             &[],
             &namespace_descriptions,
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
             /*code_mode_only*/ true,
         );
 
@@ -1071,6 +1083,7 @@ bar"
             ],
             &[],
             &BTreeMap::new(),
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
             /*code_mode_only*/ true,
         );
 
@@ -1106,6 +1119,7 @@ bar"
             &[],
             &[deferred_tool],
             &BTreeMap::new(),
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
             /*code_mode_only*/ true,
         );
 
@@ -1127,6 +1141,7 @@ bar"
                 output_schema: None,
             }],
             &BTreeMap::new(),
+            crate::DEFAULT_EXEC_YIELD_TIME_MS,
             /*code_mode_only*/ false,
         );
 

codex-rs/core/config.schema.json

@@ -458,6 +458,9 @@
             "code_mode": {
               "$ref": "#/definitions/FeatureToml_for_CodeModeConfigToml"
             },
+            "code_mode_buffered_exec": {
+              "type": "boolean"
+            },
             "code_mode_host": {
               "type": "boolean"
             },
@@ -4896,6 +4899,9 @@
         "code_mode": {
           "$ref": "#/definitions/FeatureToml_for_CodeModeConfigToml"
         },
+        "code_mode_buffered_exec": {
+          "type": "boolean"
+        },
         "code_mode_host": {
           "type": "boolean"
         },

codex-rs/core/src/session/session.rs

@@ -1137,9 +1137,10 @@ impl Session {
                         session_configuration.parent_thread_id,
                     ),
                 ),
-                code_mode_service: crate::tools::code_mode::CodeModeService::new(Arc::clone(
+                code_mode_service: crate::tools::code_mode::CodeModeService::new(
-                    &code_mode_session_provider,
+                    Arc::clone(&code_mode_session_provider),
-                )),
+                    &config.features,
+                ),
                 tool_search_handler_cache: Default::default(),
                 turn_environments: Arc::clone(&turn_environments),
             };

codex-rs/core/src/session/tests.rs

@@ -5385,9 +5385,10 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
             /*attestation_provider*/ None,
             config.http_client_factory(),
         ),
-        code_mode_service: crate::tools::code_mode::CodeModeService::new(Arc::new(
+        code_mode_service: crate::tools::code_mode::CodeModeService::new(
-            codex_code_mode::InProcessCodeModeSessionProvider,
+            Arc::new(codex_code_mode::InProcessCodeModeSessionProvider),
-        )),
+            &config.features,
+        ),
         tool_search_handler_cache: Default::default(),
         turn_environments: Arc::clone(&turn_environments),
     };
@@ -7542,9 +7543,10 @@ where
             /*attestation_provider*/ None,
             config.http_client_factory(),
         ),
-        code_mode_service: crate::tools::code_mode::CodeModeService::new(Arc::new(
+        code_mode_service: crate::tools::code_mode::CodeModeService::new(
-            codex_code_mode::InProcessCodeModeSessionProvider,
+            Arc::new(codex_code_mode::InProcessCodeModeSessionProvider),
-        )),
+            &config.features,
+        ),
         tool_search_handler_cache: Default::default(),
         turn_environments: Arc::clone(&turn_environments),
     };

codex-rs/core/src/tools/code_mode/execute_spec.rs

@@ -8,6 +8,7 @@ pub(crate) fn create_code_mode_tool(
     enabled_tools: &[CodeModeToolDefinition],
     deferred_tools: &[CodeModeToolDefinition],
     namespace_descriptions: &BTreeMap<String, codex_code_mode::ToolNamespaceDescription>,
+    default_exec_yield_time_ms: u64,
     code_mode_only: bool,
 ) -> ToolSpec {
     const CODE_MODE_FREEFORM_GRAMMAR: &str = r#"
@@ -26,6 +27,7 @@ SOURCE: /[\s\S]+/
             enabled_tools,
             deferred_tools,
             namespace_descriptions,
+            default_exec_yield_time_ms,
             code_mode_only,
         ),
         format: FreeformToolFormat {
@@ -58,6 +60,7 @@ mod tests {
                 &enabled_tools,
                 &[],
                 &BTreeMap::new(),
+                codex_code_mode::DEFAULT_EXEC_YIELD_TIME_MS,
                 /*code_mode_only*/ true,
             ),
             ToolSpec::Freeform(FreeformTool {
@@ -66,6 +69,7 @@ mod tests {
                     &enabled_tools,
                     &[],
                     &BTreeMap::new(),
+                    codex_code_mode::DEFAULT_EXEC_YIELD_TIME_MS,
                     /*code_mode_only*/ true,
                 ),
                 format: FreeformToolFormat {

codex-rs/core/src/tools/code_mode/mod.rs

@@ -16,6 +16,8 @@ use codex_code_mode::CodeModeSession;
 use codex_code_mode::CodeModeSessionProvider;
 use codex_code_mode::CodeModeToolKind;
 use codex_code_mode::RuntimeResponse;
+use codex_features::Feature;
+use codex_features::Features;
 use codex_protocol::models::FunctionCallOutputContentItem;
 use serde_json::Value as JsonValue;
 use tokio::sync::OnceCell;
@@ -52,6 +54,13 @@ pub(crate) use wait_handler::CodeModeWaitHandler;
 pub(crate) const PUBLIC_TOOL_NAME: &str = codex_code_mode::PUBLIC_TOOL_NAME;
 pub(crate) const WAIT_TOOL_NAME: &str = codex_code_mode::WAIT_TOOL_NAME;
 pub(crate) const DEFAULT_WAIT_YIELD_TIME_MS: u64 = codex_code_mode::DEFAULT_WAIT_YIELD_TIME_MS;
+const BUFFERED_EXEC_YIELD_TIME_MS: u64 = 30_000;
+
+pub(crate) fn default_exec_yield_time_override_ms(features: &Features) -> Option<u64> {
+    features
+        .enabled(Feature::CodeModeBufferedExec)
+        .then_some(BUFFERED_EXEC_YIELD_TIME_MS)
+}
 
 /// Returns true for the un-namespaced code-mode `exec` tool.
 pub(crate) fn is_exec_tool_name(tool_name: &ToolName) -> bool {
@@ -68,16 +77,21 @@ pub(crate) struct CodeModeService {
     session: OnceCell<Arc<dyn CodeModeSession>>,
     session_provider: Arc<dyn CodeModeSessionProvider>,
     dispatch_broker: Arc<CodeModeDispatchBroker>,
+    default_exec_yield_time_override_ms: Option<u64>,
     shutting_down: AtomicBool,
 }
 
 impl CodeModeService {
-    pub(crate) fn new(session_provider: Arc<dyn CodeModeSessionProvider>) -> Self {
+    pub(crate) fn new(
+        session_provider: Arc<dyn CodeModeSessionProvider>,
+        features: &Features,
+    ) -> Self {
         let dispatch_broker = Arc::new(CodeModeDispatchBroker::new());
         Self {
             session: OnceCell::new(),
             session_provider,
             dispatch_broker,
+            default_exec_yield_time_override_ms: default_exec_yield_time_override_ms(features),
             shutting_down: AtomicBool::new(false),
         }
     }
@@ -88,8 +102,11 @@ impl CodeModeService {
 
     pub(crate) async fn execute(
         &self,
-        request: codex_code_mode::ExecuteRequest,
+        mut request: codex_code_mode::ExecuteRequest,
     ) -> Result<codex_code_mode::StartedCell, String> {
+        if request.yield_time_ms.is_none() {
+            request.yield_time_ms = self.default_exec_yield_time_override_ms;
+        }
         self.session().await?.execute(request).await
     }
 
@@ -371,6 +388,7 @@ mod tests {
     use codex_code_mode::FunctionCallOutputContentItem as CodeModeOutputContentItem;
     use codex_code_mode::ProcessOwnedCodeModeSessionProvider;
     use codex_code_mode::RuntimeResponse;
+    use codex_features::Features;
     use codex_protocol::models::FunctionCallOutputContentItem;
     use codex_tools::ToolName;
     use serde_json::json;
@@ -444,11 +462,12 @@ mod tests {
 
     #[tokio::test]
     async fn missing_process_host_falls_back_to_in_process_session() {
-        let service = CodeModeService::new(Arc::new(
+        let service = CodeModeService::new(
-            ProcessOwnedCodeModeSessionProvider::with_host_program(
+            Arc::new(ProcessOwnedCodeModeSessionProvider::with_host_program(
                 "codex-code-mode-host-does-not-exist".into(),
-            ),
+            )),
-        ));
+            &Features::with_defaults(),
+        );
 
         let response = service
             .execute(ExecuteRequest {

codex-rs/core/src/tools/spec_plan.rs

@@ -2,6 +2,7 @@ use crate::agent::exceeds_thread_spawn_depth_limit;
 use crate::agent::next_thread_spawn_depth;
 use crate::session::step_context::StepContext;
 use crate::session::turn_context::TurnContext;
+use crate::tools::code_mode::default_exec_yield_time_override_ms;
 use crate::tools::code_mode::execute_spec::create_code_mode_tool;
 use crate::tools::context::ToolInvocation;
 use crate::tools::effective_tool_mode;
@@ -472,6 +473,9 @@ fn build_code_mode_executors(
         .sort_by(|left, right| compare_code_mode_tools(left, right, &namespace_descriptions));
     let deferred_tools =
         collect_code_mode_exec_prompt_tool_definitions(deferred_exec_prompt_tool_specs.iter());
+    let default_exec_yield_time_ms =
+        default_exec_yield_time_override_ms(&turn_context.config.features)
+            .unwrap_or(codex_code_mode::DEFAULT_EXEC_YIELD_TIME_MS);
 
     vec![
         Arc::new(CodeModeExecuteHandler::new(
@@ -479,6 +483,7 @@ fn build_code_mode_executors(
                 &enabled_tools,
                 &deferred_tools,
                 &namespace_descriptions,
+                default_exec_yield_time_ms,
                 tool_mode == ToolMode::CodeModeOnly,
             ),
             code_mode_nested_tool_specs,

codex-rs/core/src/tools/spec_plan_tests.rs

@@ -1071,6 +1071,20 @@ async fn code_mode_only_exposes_code_executor_and_hides_nested_tools() {
     );
 }
 
+#[tokio::test]
+async fn code_mode_buffered_exec_updates_exec_description() {
+    let plan = probe(|turn| {
+        set_features(turn, &[Feature::CodeMode, Feature::CodeModeBufferedExec]);
+    })
+    .await;
+
+    let ToolSpec::Freeform(exec) = plan.visible_spec(codex_code_mode::PUBLIC_TOOL_NAME) else {
+        panic!("expected code mode exec tool");
+    };
+    assert!(exec.description.contains("Defaults to 30000 ms."));
+    assert!(!exec.description.contains("Defaults to 10000 ms."));
+}
+
 #[tokio::test]
 async fn code_mode_only_exposes_configured_dynamic_namespace_directly() {
     let plan = probe_with(

codex-rs/features/src/lib.rs

@@ -92,6 +92,8 @@ pub enum Feature {
     // Experimental
     /// Enable JavaScript code mode backed by the in-process V8 runtime.
     CodeMode,
+    /// Use a 30-second default yield timeout for code mode exec calls.
+    CodeModeBufferedExec,
     /// Run JavaScript code mode in the standalone host process.
     CodeModeHost,
     /// Restrict model-visible tools to code mode entrypoints (`exec`, `wait`).
@@ -859,6 +861,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::UnderDevelopment,
         default_enabled: false,
     },
+    FeatureSpec {
+        id: Feature::CodeModeBufferedExec,
+        key: "code_mode_buffered_exec",
+        stage: Stage::UnderDevelopment,
+        default_enabled: false,
+    },
     FeatureSpec {
         id: Feature::CodeModeHost,
         key: "code_mode_host",